The Contribution of Reactive Halogen species to the Oxidation Capacity of the Troposphere-Reactive Halogen species: cycles - mechanisms - and field observations

Dettagli del progetto

Costo totale:

Contributo UE:

Coordinato in:

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Meccanismo di finanziamento:

CSC - Cost-sharing contracts

Obiettivo

To study the tropospheric abundance, reaction cycles, loss processes, and effect of Reactive Halogen Species in the troposphere, in particular with respect to their influence on the total oxidation capacity of the troposphere (marine and

This study is a contribution to the part of the programme dealing with the Oxidation Capacity of the Troposphere. It will be achieved by coordinated field-, laboratory- and modelling investigations of reactive halogen species, their precursor and storage species, and the reaction mechanisms involved. Field measurements will include direct determination of halogen oxides by Differential Optical Absorption Spectroscopy (DOAS) at sub-ppt levels. The laboratory studies will close many gaps in our knowledge of RHS related homogeneous and surface-catalysed reactions including iodine chemistry. The latest data from field and laboratory studies will be assembled in trajectory- and limited area 3D models, which will help to understand the results of the field campaigns as well as to assess the regional and global impact of RHS chemistry. A further important part of this study will be the assessment of a possibly anthropogenic influence on RHS sources and the transformation mechanisms within the RHS reservoir. Thus possible mechanisms changing the tropospheric oxidation capacity due to human activities can be investigated. While a central question concerns the importance of release of RHS from sea salt aerosol, for instance due to reaction of anthropogenic NOy species (like N205, NO2) with sea salt aerosol, the detailed investigation of those processes is the aim of a parallel study with the sub-title "Sea Salt Aerosols: Laboratory Investigation of Heterogeneous Halogen Activation in the Troposphere (HALOTROP-SALT)". Areas where enhanced levels of RHS are to be expected (like polluted coastlines or polar regions) will be identified. Regional processes involving RHS will be set into a global perspective.